Return BIGINT from ROWNUM(), ROW_NUMBER() and rank functions

cleanup StringUtils.cache

Minor changes in parser and documentation

1. No need to call `hashCode` if  `cache=null`
2. Remove redundant `null` comparison. `String.equals` will anyway return `false`

Remove SysProperties.CHECK preconditions around simple assertions

Improve SQL Standard compliance in LOB precision parsing

DBSettings.optimizeIsNull removal and other minor changes

Use multi-catch java 7 language construction to simplify code

Improve cost calculation for multi-column indexes